"It was a bright cold day in April, and the clocks were striking thirteen."
Use this secret phrase to get access to Nxt account holding all the coins. Now you have all the keys you were looking for, what's next?
Sorry, I don't follow you?
In the very beginning Nxt had all the coins kept on a single account that is accessible through that phrase.
This attack doesn't work that way. It relies on contemporary private keys, from very recent history.
And this appears to contradict your conclusion. If you need a matched set of keys all having large balances from very recent history, then this is either impossible or very expensive.
Especially if there is a one day timeframe.
Since it needs to be a recent set of privkeys all with large values, it almost seems to be provable that is it impossible, unless the coin's liquidity is 20% of total marketcap per day. How would it be possible for all large stakeholders to go from being large stakeholder to not having any in a very recent history timeframe?
THAT is the fatal assumption in your attack when combined with being able to buy such keys for below market value.
I can postulate a similar nearly costless attack by saying I will just by all the mining equipment for scrap values from all the large miners right after they upgrade. Since I am buying it from all of them, even though the hardware is slower, I will have more hashpower than any of them. 51% attacker is in the bag. It will be so easy to get them to sell me their useless mining equipment for $500
Or maybe not?
A large stakeholder doesnt immediately become a non-stakeholder. Most all cases it is a gradual process.
James